The abnormalities in the regulation of lipid biosynthesis in fresh cells in short term culture and in cell lines derived from genetically abnormal human subjects will be studied and compared with comparable cells from normal subjects. Particular emphasis will be placed upon the study of the accumulation of cholesteryl ester in both lymphocytes and monocytes. The regulation of the low density lipoprotein receptor will be studied by incubations in media with radio-iodinated low density lipoprotein. The conversion of circulating monocytes to macrophages in culture will provide an additional cell line for study. A highly sensitive, reproducible method for the detection of small quantities of tocopherol (2 nanograms) has been developed using high performance liquid chromatography and fluorescence spectrophotometry. The exchange of tocopherol between chylomicrons and cellular elements of the blood will be studied in hyperlipidemic subjects and in individuals ingesting large amounts of Vitamin E.